This paper addresses the problem of controller design for constrained
robots. A control algorithm, described as a combination of the direct
adaptive and the variable structure method, is presented for the traje
ctory tracking of an end-effector on a constrained surface with specif
ied constraint forces. This scheme has certain advantages, both with r
espect to computational efficiency and with respect to design. With re
spect to computational efficiency, the calculation of the regressor is
avoided. With respect to design, since the number of parameter update
laws required in the adaptation is independent of the number of links
of the robot, the difficulty of tuning numerous adaptation gains is a
voided.